Question 1Warm-upFoundation
How much energy is needed to melt 2 kg of ice at 0 °C? (Specific latent heat of fusion of ice = 334 000 J/kg)
E = mL.
Worked solution
- J
Answer: J
GCSE & IGCSE physics practice
Specific latent heat questions and answers
Specific latent heat, , is the energy needed to change the state of 1 kg of a substance without changing its temperature: . Melting uses the latent heat of fusion; boiling uses the latent heat of vaporisation. The last questions combine it with , a classic multi-step exam question.
8 questions · Foundation tier · Every answer is checked as you type it, with a full worked solution. Updated .
Where specific latent heat comes up
| GCSE (AQA) | Physics and Combined Science, Foundation and Higher. E = mL is given on the equation sheet (select and apply). |
|---|---|
| Cambridge IGCSE (0625) | The 2026 to 2028 syllabus covers melting and boiling without a temperature change, but has no specific latent heat calculation. |
The method
- E = m × L: energy in J, mass in kg, L in J/kg.
- Rearranged: m = E ÷ L and L = E ÷ m.
- Fusion: solid ↔ liquid. Vaporisation: liquid ↔ gas.
- For heating and then a change of state, add the two energies: mcΔθ + mL.
Specific latent heat questions
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Warm-up
Question 2Warm-upFoundation
How much energy is needed to boil 0.5 kg of water at 100 °C? (Specific latent heat of vaporisation of water = 2 260 000 J/kg)
E = mL.
Worked solution
- J
Answer: J (1.13 MJ)
Exam-style
Question 3Exam-styleFoundation
It takes 46 000 J to melt 0.2 kg of a solid at its melting point. Calculate its specific latent heat of fusion.
L = E ÷ m.
Worked solution
- J/kg
Answer: J/kg
Question 4Exam-styleFoundation
167 000 J of energy is used to melt ice at 0 °C. What mass of ice melts? ( J/kg)
m = E ÷ L.
Worked solution
- kg
Answer: kg
Question 5Exam-styleFoundation
How much energy is needed to melt 250 g of ice at 0 °C? ( J/kg)
250 g = 0.25 kg.
Worked solution
- J
Answer: J
Question 6Exam-styleFoundation
A 2.26 kW kettle keeps boiling water for 100 s after it reaches 100 °C. What mass of water turns to steam? ( J/kg; assume no energy is wasted)
Energy = power × time, then m = E ÷ L.
Worked solution
- J
- kg
Answer: kg (100 g)
Challenge
Question 7ChallengeFoundation
How much energy is needed to turn 1 kg of ice at 0 °C into water at 20 °C? (Ice: J/kg; water: J/kg °C)
Melt it first (mL), then warm the water (mcΔθ).
Worked solution
- Melting: J
- Warming: J
- Total J
Answer: J
Question 8ChallengeFoundation
During melting, a temperature–time graph has a flat section. Why doesn't the temperature rise even though energy is being supplied?
Temperature depends on the particles' average kinetic energy.
Worked solution
- During a change of state, the energy supplied separates the particles (breaks bonds).
- Their average kinetic energy, and so the temperature, stays the same until the change of state is complete.
Answer: The energy breaks the bonds holding the particles in place, so it goes into internal (potential) energy, not kinetic energy
Common mistakes
- Using a temperature change in E = mL (there isn't one).
- Mixing up the latent heats of fusion and vaporisation.
- Leaving mass in grams.
Stuck on one of these?
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Sources
The questions are our own. The “where it comes up” notes are from each board's published specification, checked on 27 October 2026:
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